1Mb 0.41 µm2 2T-2R cell nonvolatile TCAM with two-bit encoding and clocked self-referenced sensing

This work demonstrates the first fabricated nonvolatile TCAM using 2-transistor/2-resistive-storage (2T-2R) cells to achieve >10x smaller cell size than SRAM-based TCAMs at the same technology node. The test chip was designed and fabricated in IBM 90nm CMOS technology and mushroom phase-change memory (PCM) process. To ensure reliable search operation with such compact cells, two enabling techniques were developed and implemented in hardware: 1) two-bit encoding, and 2) a clocked self-referenced sensing scheme (CSRSS). The 1Mb chip demonstrates reliable low voltage search operation (VDDmin∼750mV) and a match delay of 1.9 ns under nominal operating conditions.